Examples of technologies known in the art include Japanese Unexamined Patent Application Publication No. S60-251189A (hereinafter, referred to as “Patent Literature 1”), in which a heat storage device is recited that uses solidification heat, released when heat storage material phase changes from a liquid to a solid, as a heat source. This heat storage device includes heat storage material that releases heat when phase changing from a liquid state to a solid state, a metal strip that serves as a trigger for nucleation that promotes the phase change of the heat storage material, and a container that houses the heat storage material and the strip. When using the heat storage material as a heat source, the heat storage material is impacted by pinching the container from the outside by fingers and snap displacing the strip. Upon the snap displacing, the heat storage material is nucleated and the heat storage material phase changes from a liquid to a solid, thereby releasing the solidification heat of the heat storage material.